A 'strange connector' on a video card in a IIcx or IIci that was used with a Portrait Display (640x870) sounds very much like a (DB-)13W3 connector. This style of connector was common amongst Sun, SG and IBM workstations.

There are 13W3M/DB-15F adapter/converter cables so that the (Apple) Workstation Portrait card can drive a conventional Apple display rather than or in replacement for the Portrait Display.

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